FIG. 9 is a diagram illustrating (a photograph of) the pixel structure of an MVA-mode liquid-crystal display device 100 according to the related art. As illustrated in the diagram, in the MVA-mode liquid-crystal display device, inside the pixels, locations where the liquid-crystal alignment-restricting force is weak exist, such as at the edges of the pixel electrode. The alignment in such locations may change greatly depending on the difference between the voltage applied to the pixels in the frame currently being displayed (current frame) and the voltage applied to the pixels in previously displayed frame (previous frame). FIG. 10 is a diagram illustrating each waveform of the gate voltage, the source voltage, and the pixel voltage when the gate line is driven in the liquid-crystal display device 100 according to the related art.
In FIG. 10, the source voltage corresponding to black is 0V, while the source voltage corresponding to white is 5V (or −5V). The common voltage applied to common electrode is 0V. The first gate voltage is a high-level voltage able to sufficiently turn on the gate of the TFT. In the example of FIG. 10, the liquid-crystal display device 100 drives the gate line only once within a single frame period.
Consequently, the voltage for displaying is applied only once within a single frame period. In FIG. 10, an example of driving that changes the displayed color of a pixel from black to white is illustrated. By applying a 5V source voltage to the source electrode of the TFT and turning on the gate of the TFT, the drain voltage (pixel voltage) changes greatly from 0V (black) to 5V (white).
FIG. 11 is a diagram that explains how an afterimage occurs on the display screen in the MVA-mode liquid-crystal display device 100 according to the related art. In FIG. 11, in the previous frame, the liquid-crystal display device 100 is displaying black in a region 111 of the display screen and is displaying a neutral color in a region 112 disposed around the region 111. Additionally, in the current frame, the liquid-crystal display device 100 changes the entire display screen to white. In this case, the voltage applied to the pixel electrodes in the region 111 is changed from 0V (black) to 5V (white). On the other hand, the voltage applied to the pixel electrodes in the region 112 is changed from 2.5V (neutral) to 0V (white).
In the current frame, since the amount of change in the voltage applied to the pixel electrodes is small in the region 112, the alignment is not disturbed much in the locations of weak alignment-restricting force inside the pixels. Consequently, in the region 112, an afterimage does not occur, and white is displayed correctly. On the other hand, in the current frame, since the amount of change in the voltage applied to the pixel electrodes is large in the region 111, the alignment is disturbed greatly in the locations of weak alignment-restricting force inside the pixels. Because of this, in the current frame, a phenomenon occurs in which the brightness of the pixels in the region 112 becomes different than the brightness of the pixels in the region 111. As a result, the display color of the region 112 is influenced by the black in the previous frame, and is no longer displayed as white. Because of this, an afterimage of the color of the previous frame occurs in the region 111.
PTL 1 discloses a drive circuit of an active-matrix liquid-crystal display device provided with a plurality of video signal lines for respectively transmitting a plurality of video signals expressing an image to be displayed, a plurality of scan signal lines that intersect with the plurality of video signal lines, and a plurality of pixel-forming parts disposed in a matrix, each corresponding to an intersection point between the plurality of video signal lines and the plurality of scan signal lines, the drive circuit comprising: a scan signal line drive circuit that selectively drives the plurality of scan signal lines such that each scan signal line is selected during a preliminary charging period preset for each scan signal line and during a main charging period preset as a period after the preliminary charging period; and a video signal line drive circuit that applies a voltage obtained by adding a predetermined voltage to a voltage for expressing the image to be displayed to the plurality of video signal lines in an overlapping charging period that, in the main charging period for each scan signal line, overlaps with the preliminary charging period for a scan signal line other than each scan signal line, and applies the voltage for expressing the image to be displayed to the plurality of video signal lines in a period other than the overlapping charging period in the main charging period for each scan signal line, wherein the overlapping charging period for each scan signal line is a partial period in the main charging period for a scan signal line other than each scan signal line, and corresponds to a predetermined period from the start of the main charging period. Furthermore, PTL 1 also discloses that, according to the drive circuit, it is possible to provide a highly responsive liquid-crystal display device capable of achieving greater power savings, reduced size, and lowered costs.
PTL 2 discloses a liquid-crystal display device provided with: a plurality of pixels arranged in a matrix, each including a pixel electrode for applying a voltage to a liquid crystal placed between the pixel electrode and a counter electrode, and a switching element connected to the pixel electrode; a plurality of scan lines arranged in a column direction, which are commonly connected to the switching elements in a row direction; and a vertical scan circuit that supplies a scan signal controlling the switching elements between a conducting state and a non-conducting state to scan the pixels sequentially by each scan line. The scan signal includes a first conducting signal that sets the switching elements to the conducting state; a second conducting signal that sets the switching elements to the conducting state later than the first conducting signal, and a non-conducting signal that sets the switching elements to the non-conducting state between the first conducting signal and the second conducting signal. During a period in which the second conducting signal is being applied to a predetermined scan line, the vertical scan circuit applies the first conducting signal and the non-conducting signal to the scan line to be scanned next after the predetermined scan line. Furthermore, PTL 2 also discloses that, according to the liquid-crystal display device, it is possible to suppress the degradation of image quality caused by parasitic capacitance coupling between pixel electrodes and feed-through between pixels, and suppress the degradation of image quality caused by the occurrence of pixel defects over a plurality of rows.